This invention relates generally to furrow openers for grain drills or the like, and more specifically to an improved double disk furrow opener and disk blades therefor.
Double disk openers are used extensively to provide a furrow for receiving seed grains and/or fertilizer. FIG. 1 of the drawings shows a double disk opener assembly 10 typical of previous devices and used for example with the John Deere Series 8000 and 9000 Grain Drills. A pair of flat disk blades 12 are mounted for rotation on bearing screws 14 secured in tapped holes provided in a machined face of a cast seed boot 16. Each screw 14 extends through an inner race of a bearing 18 mounted within a bearing cap 20 which in turn is secured to the blade 12 by a plurality of rivets 22. The flat blades 12 form a narrow V-shaped cutting point 23 for establishing a furrow. Using flat blades 12 allows the point 23 to remain narrow so that the force necessary for the blades to penetrate the ground is minimized and so that the amount of dirt thrown away from the furrow is minimized.
To remove a blade from or secure a blade to the boot 16, a bearing plug 24 on the end of the cap 20 is removed and a hexagon or alan wrench is inserted into a hex recess in the head 28 for turning the bearing screw 14. Two wrenches are necessary to remove the two screws 24 and 14 each time a blade 12 is to be replaced. Additionally, the seed boot 16 has to be tapped to receive the screws 14 thereby increasing the cost of the assembly 10.
Preventing the bearing screw 14 from coming out of the boot 16 has been a continuing problem requiring that the screw be tightened by impact. The tapped hole often has threads that are inferior to those, for example, in a nut, and therefore the bearing screw cannot be tightened comparably to a nut and bolt assembly. Additionally, torquing the bearing screw with an alan wrench is more difficult than torquing a nut and bolt assembly with a socket or box-end wrench or the like. Loss of complete disk blade members commonly occurs as the screws 14 work loose because of vibration during transport or operation of the implement.
When a blade member such as that shown in FIG. 1 is replaced, the bearing 18 is normally replaced at the same time whether or not it is worn or otherwise damaged because it is secured to the blade 12 by the riveted bearing cap 20. Although bolts could be used to replace the rivets 22, they would have a tendency to work loose and would require additional time for removal when retrieving a bearing 18. Each cap 20 protrudes outwardly from the axis of rotation of the disk blade widening the assembly 10 and thereby decreasing the distance between adjacent assemblies which hampers the free flow of trash. When the assemblies 10 are spaced for narrow row planting, the obstruction of trash flow by the caps 20 is particularly significant since row spacing may be on the order of only about 6 inches. Small reductions in the width of the assemblies can reduce trash flow problems. Often adjacent rows will be staggered front-to-back to increase the spacing. If staggering is used it is important that the openers cut a clean furrow without the rear openers throwing dirt on the furrow cut by the forward openers.
As is evident from FIG. 1, each blade member is fabricated from several components rather than a single piece of metal. The bearing cap 20 is difficult to fabricate and requires the additional step of riveting to the blade 12. Since the blade itself is most likely to wear out and need replacement before other components such as the bearing 18 or the cap 20, a double disk assembly design is necessary which requires no replacement of other components if only the blade is worn or damaged. It is also desirable to eliminate the bearing cap and reduce the width of the assembly so that the trash flow characteristics of the blade assemblies are improved.
In my copending application Ser. No. 908,741, now U.S. Pat. No. 4,196,779 filed May 23, 1978 and assigned to the assignee of the present application, a mounting for a single disk opener is described in which the riveted bearing cap is eliminated by mounting the bearing on a support on the implement rather than on the blade. The blade which is generally disk-shaped is secured with a single nut on a shaft which depends outwardly from the bearing. It is desirable to provide a double disk blade assembly using two bearings mounted in a similar fashion on the cast boot so that the boot does not have to be tapped for receiving a bearing screw such as shown at 14 in FIG. 1. To provide the narrow, V-shaped point 23, it is necessary that each bearing support a generally flat rather than dish-shaped blade member. A disk blade is required which can accommodate the above-described bearing while maintaining the desired V-shaped point for good furrow forming characteristics.